Gas analyzer



Aug. 31, 194s.

Filed Dec.' 29. 1945 Flai,

' G. B. BAILEY GAS ANALFIZER 2 Sheets-Sheet 1 IN VEN TOR.

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Aug.. 31; 194s. GiB. BAILEY L 2,448,206

y GAS ANALYZER Filed Dec. 29; 1943 2 Sheets-Sheet 2 @50265 E 5A/Ex INVENTOR.

Patentecl ug. 31, 1948 UNITEDr STATES PATENT OFFICE M 2,448,206 i f f GAS ANALYZER George B. Bailey, Long Beach, Ind., assignor to The rHays Corporation, Michigan City, Ind., a corporation of Indiana Application December 29, 1943, serialV No. 516,011

This invention relates to a gas analyzer, and particularly to a Agas analyzer having a valve for controlling the sequence of operations in a gas analyzer of the Orsat type.

In conventional gas analyzers of the Orsat type, a gas sample is first introduced intouthe measuring chamber to iill the same and purge residual gases from the previous operation while a leveling bottle is positioned below the burette. The gas sample is then measuredby elevating the leveling bottle to bring the liquid level in the burette to the zero point of the burette. r1`hen the leveling bottle is elevated above the burette to force the gas from the burette into the absorbing chamber to permit the gaseous constituent which isto be measured to ibe absorbed. Theresidual gas is then drawn back into the burette by lowern ing the leveling bottle to the point at which the liquid therein is at the same level as the liquid in the burette, which point or level may be read on a scale juxtaposed to the burette and calibrated, as in terms of percentage of total gas sample originally measured. Then the residual gas is expelled.

Care must be exercised in the use of the device to prevent liquid from rising above the 100% point of the burette in exhausting spent gases from the device, since this may entail loss of liquid. Also, the constructions heretofore ravailable have not been Well adapted for reading to the 100% mark. Another diiiiculty experienced has been in connection with the proper sequential operation of the control valve in a complete measuring cycle, includingthe venting operation, between completion of one measurement or analysis and the start of the succeeding analysis.

`It is the primary object of this invention to provide a gas analyzer with a control valve so constructed as to overcome each of the above mentioned difculties and objections of conventional analyzers. L

A further object is to provide a gas analyzer with a valve having a conduit portion projecting into the burette with a capillary fit therein and terminating at the 100% mark of the burette to bring gas into the analyzer at the 100% `measur.

ing point thereof and to prevent liquid from rising in the burette above said 100% point. A furtherobject is to provide a gas analyzer valve having*self-locating'means for eachl of multiple operative positions thereof and means for holding valve operation between predetermined operative limits whereby'T valve manipulation to successive operative positions is controlled in the sequence required to make a gas analysis. Other objects will be apparent from the description, drawing and appended claims.

1 Inthe drawing:

Fig. 1 is a View in front elevation of a gas analyzer using my improved valve.

Fig. 2 is an enlarged longitudinal vertical sectional detail view, taken on line 2-2 of Fig. 4.

Fig. 3 is a transverse sectional View taken on line 3-3 of Fig. 2.

Fig.V iis a transverse sectional View taken on line 4-4 of Fig. 2. I

Fig. 5 is a longitudinal vertical sectional view, similar to Fig. 2 but on a reduced scale, of a modified embodiment of the invention.

Fig. 6 is av view, similar to Fig. 2, of anotherl embodiment of the invention.

Fig. 7 is a front view of the Fig. 6 embodiment.

Referring to the drawing, and particularly to Figs. 1 to A thereof, `thernumeral I0 designates the frame of an analyzer having a horizontal platform adjacent one side thereof, a second horizontal platform I2 projecting from the opposite side thereof, and a horizontal cross bar I3 above the level of said platforms and carrying a plurality of spring clips I4. A plurality of containers I5, containing different gas absorbing chemicals, aremounted upon platform I2 and are held in place by brackets I6. Each container .I5 mounts a pipette I'I communicating therewith and held in place by a compression fitting I8 and by one of the spring clips I4. The pipettes are preferably filled with metal wool or other material capable of maintaining a wetted condition byy capillarity when the lower portion thereof is immersed in liquid. Pipettes I'I have reduced dimension necks at their upper ends connected by rubber ory like tubing I9 to a needle valve 20 -y carried by the top wall of housing I0 and positioned thereabove. v

A glass burette 2| is suitably mounted on plat-f form II and is enclosed within a glass water jacket 22 which is supported near its upper end Y, by one Yof the spring clips IIL WaterI jacket 22 is rsealed at its upper end by cap 23 iitting around thev reduced lstem or neck 24 of the upper end' of the burette, and is also sealed at its lower end by a suitable fitting or gasket 25. The lower `end of the burette 2 Iis of reduced diameter and projects through platform I I for connection with one end of an elongated flexible conduit 26 whose opposite end is connected'to the lower portion of a glass leveling bottle 2l which is -vopen at its upper end. The upper reduced neck 24 of burette 2| above cap 23 is connected with' a rubber or like tube 28 which is also connected with a neck 29 projecting from the control valve 30.

Control valve 30 is preferably of the construction illustrated in Figs. 2 to 4 and has a housing 3| from whose lower end the neck 29 depends.

Valve housing 3| has a central downwardly ta pering bore 32 communicating with the reduced diam-eter bore of neck 29. The upper portion of valve housing 3| has a reduced diameter exter- 3 nally screw threaded neck 33 which projects through an opening in the topwall of frame l, and a nut 34 threaded on said yneck serves to secure the valve in operative position on the frame. A frusto conical valve plug 35 has a snug rotatable nt in the bore 32. A reduced diametery neck 36 projects axially from the upper end ofthe- Valve plug and terminates in an enlarged flange p-ortion 3l. A shaft 3S projects axially above flange 37. A coil spring 39 encircles shaft and seats upon flange 31. A ycompression nut 40, threaded on the upper end of neck 33 confines spring 39 and regulates the pressure exerted by spring 39 to properly seat the valve plug in bore 32. Shaft 36 projects through compression nut 4t and mounts a knob 4l on its upper end, held in place by set screws/A42.

The valve plug 35 has a plurality of recesses 43, here illustrated as four in number, formed in its periphery adjacent its upper end and lying in a common plane transverse thereof. l.A radial bore 44 is formed in the valve housing 3i in the same transverse plane as recesses 43. A ball 45 is mounted in the inner end of said bore and is pressed against the valve body 3g by a spring 4ty confined in said bore by a set screw 41. A stop member 48 is screw threaded in the neck 36 of the valve plug and has an enlarged head 49 adapted to engage the inner end of a .set screw t threaded in the valve housing 3l to limit the rotation of the valve plug S5 in the valve housing to less than 360. The set screw 5l] and stop head 49 are so proportioned and positioned with respect to recesses 43 in the valve plug that ball 45 'may reseat successively in each of said recesses during rotation of the valve plug between its lopposite limits of rotation as determined `by said stop 49 and Is'et screw 5l).

The lower end of the plug valve mounts an elongated axial conduit 5I which extends downwardly therefrom through neck 29 and tube 23 vand into the reduced diameter upper neck 24 of the burette 2 l. The valve plug has an axial bore 52 formed in the bottom portion thereof and communicating with conduit 5l. A transverse or radial bore 5'3 is formed in the plug to communicate with the upper end vof bore 52 and is connected with a header or conduit 55 yprefer'- ably having a capillary bore and which lextends to and is connected with the needle valves 20. Another radial bore 56 is formed in the Valve housing 3l at the same level and at angle to bore 54 and communicates with a tubul-ar fitting 57 carried by the valve housing. An elongated Flexible tube 58 is connected `with fitting 51 rand has an aspirator bulb 59 interposed therein, said bulb preferably being provided with a check valve (not shown), whereby it serves as a Apump for forcing a gas sample into the burette.

The valve housing 3l is provided with a radial bore 6D at a different level than bores 54 and 56, and in angular relation thereto. A longitudinal bore Bl is formed in the lower end of valve plug 35 in spaced relation to the axis thereof, and a radial bore 62 is formed in said plug at the saine level as bore 6D and communicates with the upper end of bore 5 I.

In the use of the device, the free end of tube 58 is inserted into the space, as a stack, whose gaseous content is to be analyzed; t-he valve knob is set for registration of bores 53 and 56; and the leveling bottle 2l is positioned at a level below the burette. The aspirator bulb is then operated to pump gas through tube 58 'and the valve Sil into the burette 2l. When a sample has been taken, the valve knob is rotated to the proper angle to effect registration of the bores 62 and 50, which vents the burett'e to insure against a gas :pressure the-rein which exceeds atmospheric pressure. The valve knob is then turned to a third position in which the valve is fully closed and 'the levelling bottle 21 is raised until the liquid therein and in the burette 2l assume the level,v

Ltherebynoeasuring the volume of lgas in the burette. The valve is then turned to a fourth lp0- sition, illustrated in `Figs. 2 and 3, establishing registration of bores V53 and 54, and the leveling bottle is raised to force the gas sample into a selected one of the absorbing pipettes il for absorption of a selected constituent of the gas sample. All of the valve adjusting movements of the knob thus far described have been in one direction, i. e., clockwise as viewed in Figs. 3 and 4, and th-e stop head 49 assumes the position illustrated in Fig. 4 relative to set screw 5t whereby further rotation in that direction is prevented. Knob 4l is then turned in the reverse direction to the same position as for the measuring ope-ration, and the leveling bottle is lowered to again bring the liquid therein to the same level as the liquid in the burette, which level determines the percentage of the gas -which has been absorbed, i. e., percentage of the constituent of the gas for which the test is being made, when compared to the initial measurement of level with reference to the scale 63 which may be etched upon the burette as shown in Fig. l or may be provided upon a separate member 64 juxtaposed to the burette, as illustrated in Fig. 2. Then the knob is turned to a sixth position corresponding to the second position, bringing bores G2 and Gouinto register to permit the spent gases to be expelled .by again elevating the leveling bottle. Then the knob is returned to the lstarting rposition for registration of bores 53 and 56. At this starting position the stop head 49 assumes the position illustratedin dotted lines in Fig. 4 relative to lset screw 5B, thereby preventing further rotation of the knob in the return direction, i. e., counter-clockwise as viewed in Fig. 4. The operations described above are those required for analysis of a sample for one constituent only, and where more than one constituent is to be determined, additional operations to force the sample into other selected pipettes and to take measurements must be made before the Venting or purging operation, 'as will be apparent.

The accurate positioning of the valve at each of the successive operative stations is facilitated by the arrangement of spring pressed lball 45 and recesses 43. Thus, the operator can turn the knob until he feels the snap seating of the ball in the succeeding recess '43, and he i's assured that the valve is in desired adjustment. Also, the ball and recess arrangement prevents accidental displacement of the valve vfrom its required setting during the performance of the step of the analyzing method for which said valve setting has conditioned the apparatus. The ycombination of the stops 49,-50 and of the auto-matic port-registering snap lock arrangement 43-45 greatly simplifies operation of the device and minimizes the possibilities that error may occur from failure to 'follovi'l the required sequence of operations or to effect the proper sequence of valve adjustment. l 1

The connection 'of the valve and burette, and particularly the arrangement of parts at said connection, is of vlgreat importance in this device. Thus the clearance between the inner surface of 5. theneck 24A of the Iburetteand the outer surface off-fthe conduit s :depending from the ivalvev shouldbe of capillary dimension,.preferably about .020bfl an inch, in order to :permit gasto pass.

around conduit 5| .and to restrainsliquidrsuch as water, from passing between saldparts under 1 normal operating conditions. f. I v. i. :By this arrangement, the liquid in the burette will notfpass upwardly and out fof thetvalve at the venting bore 60 in the normal gas-exhausts.

embodiment that gas in the passage v12 is vnever Y. pushed-'over into the absorbing pipette. f The gas ingaoperation. The termination of the'conduit Y '5|4 at 'the Vlevel of the 100% mark onthe scale is alsol important, since it permits.accuratefread. ling of the resultsv of the analysis'I up to 100%.

Note'also that the combined, features kof capillary when `the vnext cycle is started, being replaced f by fresh. gas inthe passage du-ring the gas measuring step of the succeeding cycle. `Obwhose axis is horizontal.

Whichiscontained in this passagel is trapped therein during theentire operation, so? itad'oesn't .enter into' theoperatlon of the analyzer atf'all'. The factA that gas is Iso trapped in passage 12 .does necessitate the raisingl of the liquldlevel in the-devicetothe full level vof valvel -10,`land to be certain'.ofwac'curate results, it may? -befadvisable to dischargeza small amount ofthe'liquid fromlthefleveling bottle through the outlet 1| in eachgas` expelling or exhausting step'in the use fof 'the apparatus. This will require refilling fof the leveling bottle from time to time, butis not an important consideration, especially where th liquidused in said bottle is water.V I

Another modified` embodiment of the invention is` shown in Figs.t Gand '7. This embodiment illustrates aV horizontally disposed valve whose housing 80 has a tapered bore or chamber 18| Tapered valve? 'plug i 82 is' rotatable in said bore and is resilientlyfY urged y to.' seated `"position by coil spring 83 pressing against-and heldin'place by cap 84 threaded on the front end of-thevalvehousing. 11A-stem^85 v projects fromvthe'front end of they valve plug and through a central opening in 'cap 84. `A knob 86 -is mounted on the outer end of stem 85.

viously,lthis is the equivalenty of a vcondition wherein the 4gas in the burette-in the measuring step isl all fresh gas, and-that insaidipassages is inert, since `the `passages .communicatev with the burette,v and as .long as the-volume of inert gas at atmospheric pressure is known ,to be equal tothe volume or cubic capacity ofy the passage, the actual. location of the inert gas inthe communicating spaces during thefmeasuring operation is not important.. l rv e The construction illustrated in Fig.y 5 is` an alternativet embodiment rof 'the invention which utilizes a Aconventional three-way valve 110 which may have' three consecutive operative, positions as the handleis moved in .either direction between `rthe limits of'i-ts movement, i.1e.', a gas transfer position, a venting position and a closed plurality of notches f 81. are formedlfinfthe periphery .of `'valve plug 82 incircumferentially spacedrelatin at the small diameter end there of. vAi transverse bore in the valvehousing mounts a. ball 88 rat its inner end1to'f 4seatin notches 81, 'saidball '.-being pressedlinwardlyby spring 89 which is,.retained in placeiby :the="set screwy 90, A pin 9| projects radiallyintorbore 8| in spaced relation to the small diameter :end of Lvalve plug 82 .andis engagea-ble by longitudinally extending :pin- 92 .projecting from the-fend the adjacent largediameter end of thevalve plug;

lAnother radial'bore 96, preferably parallel'tob'ore position.'V Valve 10 has a nipple 1| adapted for connection with theaspirator tube through which a gas sample is supplied to the valve, and has an elongated conduit 12 dependingftheref-rom and extending into the neck A24 'at rtheupper end of burette 2|. Conduit 12fl'1`asthe- 'same capillary cle-arance, i. e.,approximately .020 ofl an inch',"within the neck of the burette, and lterminates at the level of the 100% markon ythe scale 64 of Vthe burette as in the preferred 'em- The conduit 12 passes through a chambered fitting 13y having an externally screw threadedwneck 1.4 passing throughthe topwall o'fffframe |0 and mounting a nut 15 bearing against the upper face of said frame wall. The lower end of fitting 13 has a depending reduced diameter Aprojection 16 connected withl burette neck A24 by means'of a tube11 of rubber or likel material. Header which leads tol the valves controllingthe absorbing pipettes is: connected with fitting 13 in communicationwith a. bore 18 through the wall of said fitting. .v y y L This embodiment possessesthe-s'ame Vadvantages .above youtlined with reference tothe embodimentl shown in Figs. 2 to 4 in allrespects except .the self-locating andother structural features of lthe-plug typevalve. `.It ywill Valso benoted inxthis 93and longitudinally spaced therefrom, is formed ori-the same radius ofthe `valve body. Bore96 communicates Ywith a'conduit 91 whichleads to kthe 'header-(not shown) and the absorbing pipettes.; In diametrically'opposed relation to'bores 93 and ,96 vvand at a-.longitudinal point between saidbores, a radial bore 98 is formed inithevalve body@ The vbore isofxstepped shape, with .the inner small .diameter portion thereof mounting the end Yof adepending tube 9 9 which projects into the neck of the burette |00 with a capillary clearance, i. ke.,.a.pproximately .020 of an inch, `to terminateatfthe.100% level of the burette. scale |0l. .A sleeve` |02is secured to the valve housing v8|y concentricwith tube 9,9 to vprovide a small attirance diagonally through the valve plug in aradial plane 90 displaced from passagesS and lcwith: its ends adapted to register with bores 93 and 98 at oneoperative position ofthe: valve plug-1 Another transversepassage jl Hl extends diagonally `through the va-lve plug in the sameradial-plane 'as passages 95 and |08,With its ends adapted to-register with bores'96 `and 98 When-plug 82 is positioned at an angle 180 displaced from thelposition shown.

Y This embodiment `of the invention has the same advantages .outlined above .relative to the Fig. 2 embodiment. Note also that thedevice is adapted for usewith a forced feedgas supply mechanism inplace of aspirator bulb 59, since -a continuous supply of vgas can be vented toa'tmospherethrough passage 95 when the valve plugis at the venting position shown. The sameconditionsachieving accuracy despite entrapment offsinall quantities of gas apply to thisembodlment as Well as to the Fig. ,27a-nd 5 embodiments.,

-I claim: o ,1,In a gas analyzer,thecombin'ation with a burette, gas pumping means 'and' gas absorbing means, of a valve interposedgbetween and connected with said burette and' said pumping and absorbing means, said `valve having yrelatively shiftable parts With selectivelyregisterable ports for controlling the iiow `of gas insaidanalyzer, and a tube communicatingv with one of said ports and projecting int-o said burette with a-capillary clearance whereby the ilimitito Which liquid can rise insaidburette is dened by the position of the bottom edge of said tubular valve portion, saidvalve parts having ports communicating with said capillary clearance andadapted tc'establish communicationbetween said burette and atmosphere. y I

`v2. VIn a gas analyzer, th'e combination With-a measuring burette, gas supplying means vand gas absorbing means, of'a fitting interposed :between i and connected with said` burette and said `gas supplying and absorbing means, said tting including a control valve having relatively shiftable ported parts for selectively controlling the flow of gas in said analyzer, and atubecommunicating with one of said Iports and extending-substantially axially into said burette, said tubular portion having. 'a capillary clearance of approximately .020 ofl anwinch yin said burette at itsxterminal` portion within said burette, one of said valve ports communicating' with said capillary clearance.

3. Inf-a gas analyzer, the :combination with a graduated .measuring burette; Agas lsupplying means and gas absorbingmeans, of `a ttinginter1 posed between and connected. with said Yburette and said gas supplying and absorbing means, said fitting including a control valve having relatively shiftable ported .parts controlling the flow of gas in said analyzer, and a tube communicating with one valve port and extending substantially axially into said burette with a clearance 'of capillary dimension and terminating at the level of the @0% graduation of said burette, one'of said valve ports communicating` 'with saidcapillary clearance. f 'i '4. In a gas analyzer, the combination with a graduated measuring burette, gas supplying means and gas absorbing means, of a :ported fitting, means connecting said fitting withv said bur-ette and said gas supplying and gasabsorbing means, a multi-port`valve element shiftable in said ltting; a conduit communicating with one -valve port and extending through 4the means connecting said tting and l'lourette,` said conduit yterminating within the `upper end of said burette atijthe graduation` thereof and-having a clearance therein of capillary size, the other Valve port communicating with said capillary clearance between said conduit and said burette, said-fitting having apport open to atmosphere with which said last'named valve port is' adapted to registera 5. In a gas analyzer, the combination with a burette, gassupplying means and gas absorbing means, `oa valve housing having a chamber and a; plurality of ports ther-ein communicating re.- spectively with said burette and gas supplying and gas absorbing means, a valve element in said chamber having a passage therein, and. a. conduit communicating with said passage and projecting into said burette with a capillary clear.- ance,`said valve4 element beingadjustable for selective vcommunication of its passage with said gas supplying` and .gas absorbing means, said valve including a selectively operable vent outlet communicating with said burette through the capillary space around said conduit. f6. -In a gas analyzer, the combination with a burette, gas supplying means and gas absorbing means, of a valve housing having a chamber therein jand'ports connecting said chamber with said burette, gas `supplying means, gas absorbing means and atmosphere, a valve element in said chamber having a passage therein selectively registerable with said gas supplying and gas absorbingmeans, and a conduit, communieating -with said passage and depending from saidavalve element and projecting within said burette. with a capillary clearance, said valve element liaving apassage communicating with thecapillary clearancebetween said conduit and burette. and'adapted lfor'registration -vvith the port in 'said-fitting which is open to atmosphere.

7. 'Inagas analyzer, the combination with a burette; gas supplying means and gas. absorbing means, of a plug-type valve having a chambered housing and a rotatable valve `element havinga plurality of operative positions in'said housing anda pairof passages therein, a cond-uit depending from said valve element in communication with 'one passageand iitting in the upper portion of ysaid vburettewith va capillary clearance, said housing having ports communicating-.With said burette,- said gas supplying meansfsaid gas absorbing means and Awith atmosphere, the passage communicating With ,saidY conduit being registerable withy said gassupplying and gas absorbing portsfand the other passage being registerable with vsaid atmospheric port and communicatingi'withv the capillary space in said bu-l rette` around said conduit. l v f.

8. Ina gas analyzerpthe combination with a burette, gas supplying means and gas absorbing means, of `a plug-type valve including` a. chambered housing having a plurality `of portstherein and a valve element rotatable in said housing and having a pair Aor" passages therein', ,means con,- necting said buretteand Agas ,measuring and. absorbinglmeans Vwith diner-ent ports of -said housing, fand a conduit communicating with. one passageof said valve element and extendingthrough the-means connecting said buretteA and housing to terminate Within said burette with a capillary clearance, the other passage communicating with said capillary clearance between said conduit and burette and being adapted for registration with a housing-port opento atmosphere.

v9. in agas analyzer, lthe combinationvwith a burette, rgas supplying means -and gas absorbing means, lof 4a Ichamberedrvalve' `housing having a plurality of angularly displaced ports, 'means fconnecting said ports with said burette and gas supplying and absorbing means, a valve element rotatable in said chamber and having a pair of passages therein each selectively registerable with certain of said ports, and a conduit communieating with one passage and projecting therefrom through one of said connecting means and into said burette, said conduit having a capillary clearance in said burette, the other passage communicating with the burette through said capillary clearance space in said last named connecting means.

l0. In a gas analyzer, the combination with a burette, gas supplying means and gas absorbing means, of a chambered valve housing having a plurality 4of angularly displaced ports, means connecting said burette and gas supplying and absorbing means with said ports, a valve element rotatable in said chamber and having a pair of passages therein each adapted for selective registration with certain of said ports, spring pressed cooperating means on said housing and element for releasably locking said parts when a lpassage registers with a lport, and a conduit connected with one passage and projecting into said b-urette with a capillary clearance, the other passage communicating with said .burette through the clearance around said conduit.

11. In a gas analyzer, the combination with a burette, gas supplying means and gas absorbing means, of a chambered valve housing having a plurality of relatively .angularly disposed ports connected respectively with said burette and gas supplying and absorbing means, a valve element rotatable in said chamber and having a pair of passages therein each selectively registerable with certain of said lports, a conduit carried by said Valve element in communication with one passage and extending into said burette with a oalpillary clearance, the other passage communieating with said burette through the clearance around said conduit, said valve element being rotatable step by step from a starting position through a predetermined angle and then reversely to starting position successively register said .passages and ports during a complete cycle of operation of said analyzer, and interengageable stop members on said valve housing and valve element to limit rotation of said valve element in each direction to the limits required in said cycle of operation.

12. In a gas analyzer, the combination With a burette, gas supplying means and gas absorbing means, of a cham-bered valve housing having a plurality of ports arranged on different radii and at spaced lpoints lengthwise of said housing, means connecting said ports With said burette, gas suplplying means and gas absorbing means, and -a valve element rotatable in said housing and having a plurality of passages therein adapted. to establish communication between said ports and to open selected ports tol atmosphere at different rotative positions thereof, the connecting means to the burette comprising a pair of concentric tubes having a small clearance therebetween, and communicating with different passages, the inner tube projecting beyond the outer tube and being adapted to t in said burette with a capillary clearance.

GEORGE B. BAILEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 744,132 Tutwiler Nov. 17, 1903 1,448,901 yMoreland Mar. 20, 1923 1,474,097 Krogh et al. Nov. 13, 1923 2,026,842 Matuszak Jan. '7, 1936 2,262,703 Stuckenholt Nov. 11, 1941 2,329,459 Dickey Sept. 14, 1943 OTHER REFERENCES Shepherd, Bur. of Standards Research Paper No. 266, 1931, pp. 122-124. 

